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hw/char: riscv_htif: Use blocking qemu_chr_fe_write_all 

The current approach of using qemu_chr_fe_write() and ignoring the
return values results in dropped characters [1]. Ideally we want to
report FIFO status to the guest, but the HTIF isn't a real UART, so we
don't really have a way to do that.

Instead let's just use qemu_chr_fe_write_all() so at least we don't drop
characters.

1: https://gitlab.com/qemu-project/qemu/-/issues/2114

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240910045419.1252277-2-alistair.francis@wdc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Alistair Francis 2024-08-13 13:32:51 +10:00
parent 2ae6cca1d3
commit 4a0e8ca322
1 changed files with 10 additions and 2 deletions
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12
hw/char/riscv_htif.c
View File

@ -217,7 +217,11 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written)
tswap64(syscall[3]) == HTIF_CONSOLE_CMD_PUTC) {
uint8_t ch;
cpu_physical_memory_read(tswap64(syscall[2]), &ch, 1);
qemu_chr_fe_write(&s->chr, &ch, 1);
/*
* XXX this blocks entire thread. Rewrite to use
* qemu_chr_fe_write and background I/O callbacks
*/
qemu_chr_fe_write_all(&s->chr, &ch, 1);
resp = 0x100 | (uint8_t)payload;
} else {
qemu_log_mask(LOG_UNIMP,
@ -236,7 +240,11 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written)
return;
} else if (cmd == HTIF_CONSOLE_CMD_PUTC) {
uint8_t ch = (uint8_t)payload;
qemu_chr_fe_write(&s->chr, &ch, 1);
/*
* XXX this blocks entire thread. Rewrite to use
* qemu_chr_fe_write and background I/O callbacks
*/
qemu_chr_fe_write_all(&s->chr, &ch, 1);
resp = 0x100 | (uint8_t)payload;
} else {
qemu_log("HTIF device %d: unknown command\n", device);